U.S. patent application number 10/987473 was filed with the patent office on 2006-05-18 for striation control for current fed electronic ballast.
Invention is credited to Timothy Chen, Timothy B. Gurin, James D. Mieskoski, James K. Skully.
Application Number | 20060103328 10/987473 |
Document ID | / |
Family ID | 35509556 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060103328 |
Kind Code |
A1 |
Chen; Timothy ; et
al. |
May 18, 2006 |
Striation control for current fed electronic ballast
Abstract
In a lamp lighting ballast which generates a lamp lighting
signal for a lamp, provided is a striation elimination circuit to
increase the lumen output frequency for elimination of visual
striations which may occur within the lamp. An even harmonic signal
generator is configured to generate an even harmonic waveform, and
an injection point is configured to receive the even harmonic
signal into the lamp lighting system. The injection point is
located at a location wherein the even harmonic signal alters the
lamp lighting signal from a symmetric signal configuration to a
high content even harmonic signal configuration prior to being
received by the lamp.
Inventors: |
Chen; Timothy; (Aurora,
OH) ; Gurin; Timothy B.; (Munson Township, OH)
; Mieskoski; James D.; (Seven Hills, OH) ; Skully;
James K.; (Willoughby, OH) |
Correspondence
Address: |
FAY, SHARPE, FAGAN, MINNICH & MCKEE, LLP
1100 SUPERIOR AVENUE, SEVENTH FLOOR
CLEVELAND
OH
44114
US
|
Family ID: |
35509556 |
Appl. No.: |
10/987473 |
Filed: |
November 12, 2004 |
Current U.S.
Class: |
315/276 |
Current CPC
Class: |
H05B 41/2858
20130101 |
Class at
Publication: |
315/276 |
International
Class: |
H05B 41/16 20060101
H05B041/16 |
Claims
1. A ballast for a gas discharge lamp comprising: a ballast circuit
for producing a lamp lighting signal having a fundamental waveform;
an even harmonic signal generator for producing an even harmonic
signal of the fundamental waveform; and means for combining the
lamp lighting signal and the even harmonic signal.
2. The ballast of claim 1, wherein the ballast circuit comprises an
output transformer having a primary winding and a secondary
winding, said secondary winding producing the lamp lighting signal,
and wherein the even harmonic signal generator comprises a
transformer having a primary winding and a secondary winding.
3. The ballast of claim 1, wherein the means for combining
comprises connecting the secondary of the even harmonic generator
transformer in series with the secondary of the ballast circuit
output transformer.
4. In a ballast which generates a lamp lighting signal for a
discharge lamp or lamps, a striation elimination circuit for
elimination of visual striations, the striation elimination circuit
comprising: an even harmonic signal generator configured to
generate an even harmonic signal; and an injection point configured
for the combination of the even harmonic signal and the lamp
lighting signal, the injection point located at a position wherein
the even harmonic signal alters the lamp lighting lumen output
frequency.
5. The striation elimination circuit according to claim 4, wherein
the even harmonic signal generator is incorporated in the
ballast.
6. The striation elimination circuit according to claim 4, wherein
the even harmonic signal is synchronized to the lamp lighting
signal.
7. The striation elimination circuit according to claim 4, wherein
the even harmonic signal generator is separate from the
ballast.
8. The striation elimination circuit according to claim 4, wherein
the ballast includes a current fed inverter circuit.
9. The striation elimination circuit according to claim 4, wherein
the even harmonic signal is injected into a secondary of an output
transformer.
10. The striation elimination circuit according to claim 4, wherein
the even harmonic signal is injected to a primary of an output
transformer.
11. The striation elimination circuit according to claim 4, wherein
the even harmonic signal generator is a variable even harmonic
signal generator variability being one of timing of the generation
of the even harmonic signal.
12. The striation elimination circuit according to claim 4, wherein
the even harmonic signal is injected via the use of transformer
windings.
13. The striation elimination circuit ballast according to claim 4,
wherein the lamp has a Krypton content in a range of approximately
40% to 75%.
14. The striation elimination circuit according to claim 4, wherein
the lamp has a Krypton content greater than 75%.
15. A method of supplying signals to a gas discharge lamp in a lamp
lighting system which eliminates visual striations from appearing
in the lamp, the method comprising: generating a lamp lighting
signal; generating an even harmonic signal combining the lamp
lighting signal and the even harmonic signal; and supplying the
combined lamp lighting signal and the even harmonic signal to the
gas discharge lamp.
16. The method according to claim 15, further including
synchronizing the even harmonic signal with the lamp lighting
signal.
17. The method according to claim 15, further including generating
the even harmonic signal is out of synchronization with the lamp
lighting signal.
18. The method according to claim 15, wherein the even harmonic
signal is supplied in an inverse proportion to the supplied lamp
lighting signal.
19. The method according to claim 15, wherein the even harmonic
signal is independent from the ballast.
20. A control circuit for providing electrical power from a source
to a gas discharge lamp, comprising: a ballast circuit for
providing ac current to electrodes of the gas discharge lamp to
generate and maintain an electric discharge therethrough; and an
even harmonic signal generator for generating a signal comprising
an even harmonic of the ac current and providing the even harmonic
signal to the electrodes of the lamp simultaneously with the ac
current, wherein a shifted waveform is provided to the lamp
electrodes for substantially eliminating visible striations.
21. The ballast according to claim 20, wherein the even harmonic
signal is synchronized with the lamp lighting signal.
22. The ballast according to claim 20, wherein the ballast includes
a half-bridge inverter.
23. The ballast according to claim 20, wherein the ballast includes
a push-pull circuit.
24. The ballast according to claim 20, wherein the ballast circuit
uses BJT switches.
Description
BACKGROUND
[0001] The present application is directed to improving the visual
appearance of gas discharge lamps, and more particularly, to the
elimination of visual striations which may occur in gas discharge
lamps.
[0002] Generally, a gas discharge lamp will have an elongated
gas-filled tube having electrodes at each end. A voltage between
the electrodes accelerates movement of electrons. This causes the
electrons to collide with gas atoms producing positive ions and
additional electrons forming a gas plasma of positive and negative
charge carriers. Electrons continue to stream toward the lamp's
anode electrode and the positive ions toward its cathode electrode
sustaining an electric discharge in the tube and further heating
the electrodes. The electric discharge causes an emission of
radiation having a wavelength dependent on the particular fill gas
and the electrical parameters of the discharge.
[0003] A fluorescent lamp is a gas discharge lamp in which the
inner surface of the tube is coated with a fluorescent phosphor.
The phosphor is excited by the ultraviolet radiation from the
electric discharge and fluoresces, providing visible light.
[0004] During operation of a gas discharge lamp, such as a
fluorescent lamp, a phenomenon known as striations can occur.
Striations are zones of light intensity, appearing as dark bands.
This phenomenon can give a lamp an undesirable strobing effect. An
example of the striation phenomenon is shown in FIG. 1, which
depicts a linear fluorescent lamp 10. In one embodiment lamp 10 may
employ Krypton (Kr) as a buffer gas to improve the efficacy of the
lamp. In FIG. 1, lamp 10 has striation zones 12 which appear as the
dark bands moving along the length of the lamp.
[0005] A variety of theories as to why striations occur have been
set forth. For example, in U.S. Pat. No. 5,001,386 to Sullivan, it
is stated that striations are believed to occur as a result of
high-frequency currents re-enforcing a standing wave of varying
charge distribution between the lamp electrodes.
[0006] Sullivan attempts to solve the striation problem by
injecting a dc component superimposed on top of a driving ac
current. A disadvantage to this technique, is the requirement that
existing typical high-frequency ballasts in the marketplace must be
removed and replaced with a unique ballast capable of injecting the
dc bias component. Also, adding the dc bias may damage the lamp, by
moving mercury in the lamp to one end, creating an unbalanced light
output. It is also suggested that increasing the crest factor in a
lamp lighting system will eliminate the visual striations. However,
increasing the crest factor may also increase the stress on a lamp,
which will lead to a shorter lamp life.
[0007] Another alternative was proposed by Kachmarik et al., U.S.
Pat. No. 6,465,972 ('972) which provides an amplitude modulation
circuit placed in operative connection with the lamp input line.
The amplitude modulation circuit is configured to periodically
modulate amplitudes of the lamp input signal prior to the lamp
input signal being received by the gas discharge lamp. Operation of
the amplitude modulation circuit results in a periodic amplitude
modulation of the lamp current to eliminate visual striations
otherwise occurring in the lamp.
[0008] Yet a further attempt to eliminate striations is proposed in
U.S. application Ser. No. 09/681,994 (U.S. Publication No.
2003-0015970A1) to Nerone. In this application a ballast is
designed to convert an AC system power source to a DC voltage on a
DC bus included within the ballast circuit. An inverter circuit is
provided in the ballast circuit in operative connection with the DC
bus to generate an asymmetric alternating current on a lamp input
line. A gas discharge lamp is in operative connection to the lamp
input line, configured to receive an asymmetric alternating
current, thereby eliminating visual striations occurring in the
lamp.
BRIEF SUMMARY
[0009] In a lamp lighting system which generates a lamp lighting
signal to energize a lamp of the system, provided is a striation
elimination circuit for elimination of visual striations which may
occur within the lamp. An even harmonic signal generator is
configured to generate an even harmonic waveform, and an injection
point is configured to receive the even harmonic signal into the
lamp lighting system. The injection point is located at a location
wherein injection of the even harmonics signal alters the lamp
lighting signal from a waveform with no or a low content of even
harmonics signal to an even harmonic rich signal prior to being
received by the lamp.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a typical fluorescent lamp having
striation zones creating a strobing effect to an end user;
[0011] FIG. 2 illustrates a half-bridge current fed inverter
ballast circuit incorporating the visual striation elimination
circuit according to the present application.
[0012] FIG. 3 depicts a harmonics free lamp lighting signal
generated by the ballast system, without striation control;
[0013] FIG. 4 sets forth a choke signal of a current fed inverter
circuit such as in FIG. 2;
[0014] FIG. 5 depicts the waveform of FIG. 3 with portions of the
choke waveform of FIG. 4;
[0015] FIG. 6 shows the combination of the waveforms of FIG. 3 with
FIG. 4 supplied to the lamp where the striation control signal and
power single are integrated;
[0016] FIG. 7 illustrates a lamp lighting system where the even
harmonic signal is derived from the power factor correction portion
of the lamp lighting system;
[0017] FIG. 8 provides another embodiment of a lamp lighting system
where the even harmonic signal generator is separated from the lamp
lighting circuit, where the even harmonic signal may be applied to
the ballast generated lighting signal in a non-synchronized
manner;
[0018] FIG. 9 depicts the even harmonic signal when it is not fully
synchronized with the fundamental ballast lamp lighting signal.
[0019] FIG. 10 depicts the concept of the even harmonic generator
of FIG. 8 being a variable generator wherein the degree of
non-synchronization between the even harmonic signal and the lamp
lighting signal created by the ballast is variable;
[0020] FIG. 11 depicts a further embodiment of a lamp lighting
system wherein a ballast lighting signal sensor is incorporated
into the ballast circuit to sense the value of the lighting signal,
and this sensed value is then used by the variable harmonic
generator which alters the value of the even harmonic signal;
and
[0021] FIGS. 12 and 13 show the value variability of the even
harmonic generator of FIG. 11.
DETAILED DESCRIPTION
[0022] As depicted in FIG. 1, striation zones 12 cause an
undesirable visual effect to an end user. In addressing this
problem, it was considered the striations occur due to the
repetitiveness of the input signal supplied to the lamps, which
reinforce a standing wave of varying charge distribution between
the lamp and electrodes.
[0023] Previous attempts to limit striations as described in the
Background, commonly addressed striations which occurred during a
dimming of a lamp. However, striations are now occurring when lamps
are being operated at high or 100% output power and while at room
temperature. A primary cause of striations occurring in these
situations is due to the use of higher percentages of Krypton (Kr),
which is employed as a buffer gas to improve the efficacy and
usefulness of the lamps. For example, lamps may now have a content
of approximately 40% to 70% or more of Krypton (Kr).
[0024] Therefore, the concepts of the present application are
intended to address both striations which occur due to dimming, as
well as when the lamp is not being dimmed. In addressing this
matter, it has been determined that it is desirable to create a
high even harmonics content with respect to the fundamental
waveform, to increase the striation frequency above the range a
human eye is able to detect the effect (striation). Typically, this
frequency is greater than approximately 40 Hz. It is to be
appreciated that, while the following description is beneficial for
lamps having high Krypton content, it is also effective for lamps
having other Krypton content percentages or other buffer gases, as
well as for use with lamps which are being dimmed.
[0025] Turning to FIG. 2, illustrated is a particular circuit in
which the concepts of the present application may be employed. It
is to be appreciated, however, the concepts described herein are
not intended to be limited only to such a circuit, and may be
employed in other lamp lighting control circuits. That having been
said, FIG. 2 is a half-bridge current fed ballast 20 in which
striation control is incorporated. The half-bridge current fed
ballast 20 includes an upper switching configuration 22, and a
lower switching configuration 24. These switching configurations
include switches such as BJTs 26 and 28 respectively, driven by an
upper BJT control network 30, and a lower BJT control network 32.
Upper control network 30 includes zener diode 30a, capacitor 30b,
diode 30c, diac 30d, diode 30e, resistors 30g, 30h and diode 30i.
Lower control network 32 includes diode 32a transformer windings
32b and 32c, resistors 32f and 32g, and diode 32h. For a more
detailed discussion regarding operation of these components,
reference may be made to commonly assigned U.S. Ser. No. 10/667,545
entitled Voltage Controlled Start-Up Circuit for Electronic
Ballast, filed Sep. 22, 2003, hereby incorporated by reference in
its entirety.
[0026] An output transformer system 34, including base drive
windings 34a, 34b, primary winding 34c and secondary winding 34d,
provides output signals to lamp connectors 36. Additional
protection and control circuitry such as transit network 38
including transits 38a, 38b and 38c and a voltage input network
including resistors 42a, 42b and 42c are further provided in the
circuit.
[0027] The half-bridge circuit 20 shown in FIG. 2 is designed as a
current fed inverter ballast. A current fed transformer of the
circuit comprised of windings 44, 46 and 48 is used to generate
current for circuit operation. The present development employs a
winding 50 coupled to the current fed transformer 44, 46, 48 to
supply an even harmonics signal for the lamps. The even harmonics
signal is injected into a secondary winding 34d of the output
transformer 34 on the lamp side of the system, via coupled winding
50. The even harmonic signal is derived from the fundamental
waveform of the signals generated by the switching operation of
half-bridge circuit 20.
[0028] In one embodiment, it is noted the coupled winding signal
can alternatively be injected into the primary side 34c of the
output transformer 34. Thus, depicted is a striation control
circuit which employs an even harmonic signal that is, in this
embodiment, derived from the current transformer windings (current
fed chokes) 44, 46 and 48 that is subsequently injected into the
circuit at a secondary winding (e.g., injection point) 50 via the
described act of inductive coupling. The injected signal is free of
a DC component and is rich in harmonics, and there is not a need
for a conversion circuit. In addition, in this embodiment, the
injected signal is synchronized with the fundamental waveform
(i.e., lamp lighting signal) of the inverter ballast circuit. The
injection winding 50 also provides circuit isolation.
[0029] Thus, while it is appreciated that FIG. 2 shows the even
harmonic signal injected on the secondary side (34d) of the output
transformer 34 in FIG. 2 (i.e., the lamp connector side 36), the
present application is also effective if the injection of the
signal is on the primary side (34c) of the output transformer.
[0030] As previously discussed, FIG. 2 illustrates that the present
concepts are suitable for current fed inverter ballasts,
particularly for half-bridge ballast inverters. However, this is
not intended to limit the present concepts to the circuit of FIG.
2, but rather the concepts may be used in other circuit control
such as other current fed ballast circuits, including a push-pull
current fed ballast inverter as well as voltage fed series resonant
ballasts. The design is useful for high content Krypton mixture
fluorescent lamps used in non-dimming or dimming applications.
[0031] Turning to FIGS. 3-6, the actions occurring by operation of
circuit 20 of FIG. 2 are set forth in greater detail. Initially, in
a circuit such as circuit 20 of FIG. 2 without the injected even
harmonic signal and with switches 26 and 28 operating at
approximately equal on and off times (i.e., a 50% duty cycle), a
substantially sinusoidal lamp lighting signal 60, having no offset
(i.e., the positive signal portions 62 are equal to the negative
signal portions 64 of the signal 60) is developed. Striations may
occur in these situations where there is high Krypton content
and/or dimming of a circuit occurs. With further attention to
operation of the present concepts, the even harmonic portions of a
choke signal (also called the even harmonic signal) 66, generated
by the current transformers 44, 46 and 48 is set forth in FIG. 4,
and appears as something equivalent to a rectified AC output signal
with signal portions 68a, 68b and 68n without a DC component. Choke
signal 66 is injected (i.e., inductively coupled) at injection
winding 50 to be part of the signal supplied to the lamps, as
illustrated for example in FIG. 5. By adding the even harmonics
signal 68b of choke signal 66 to the positive going signal portion
62 of signal 60 and adding signal portion 68a to the negative going
portion 64 of signal 60, an offset lamp input signal 70 such as
shown in FIG. 6 is generated. Offset lamp input signal 70 will have
an increased positive portion 72 and a decreased negative portion
74 when compared to lamp lighting signal 60 of FIG. 3. Thus, where
signal 60 of FIG. 3 supplied only odd harmonics to a lamp,
harmonics signal 70 of FIG. 6 is designed with both even and odd
harmonics. The input signal 70 of FIG. 6 is therefore provided to
lamps to eliminate the discussed visual striations. It is to be
appreciated choke signal 66 is synchronized with the fundamental
signal 60 as they each are generated from the same input source.
Therefore, in this design, synchronization is automatic due to the
injected even harmonic signal 66 being generated by components in
the same circuit, as the components generating the lamp lighting
signal 60.
[0032] As described above, supplying the even harmonic signal
generates an offset in the waveform of the lamp lighting signal
being supplied to eliminate striations otherwise observed by the
human eye. It will be appreciated that an odd harmonic signal would
not be used as it would simply increase or decrease the lamp
lighting signal in a equal amount, thereby not creating the desired
offset.
[0033] Turning to FIG. 7, depicted are concepts of the present
application employed in a lamp system 80, having an AC input 82, a
power factor correction circuit 84, along with a ballast inverter
86, which supplies lamp 88. In this design the even harmonics are
generated in the power factor correction circuit 84 and are
injected into the ballast inverter circuit 86 via input line 89. In
this design, the even harmonic signal supplied to the ballast
inverter 86 results in a combination of an odd and even harmonics
waveform of a lamp lighting signal (such as that shown in FIG. 6)
to be supplied to lamp 88.
[0034] The previous concepts described in connection with the
circuit of FIG. 3, are equally applicable to the circuit of FIG. 7.
For example, the even harmonic signal can be synchronized to the
output signal to the lamp 88 by synchronizing Power Factor Circuit,
84 and inverter circuit 86. In this example, the ballast inverter
may be the half-bridge inverter previously discussed, a push-pull
inverter ballast or other lamp control circuit which is known in
the art, including both other current fed as well as voltage fed
control circuits.
[0035] Turning to FIG. 8, illustrated is a lamp lighting circuit 90
where ballast 92 receives power from power source 94 for
application to lamp 96. In this design, an even harmonic signal
generator 98 is provided separately from the ballast 92 and power
source 94 and is injected into the ballast generated signal at
injection winding or point 100. By this arrangement, and as shown
in FIG. 9, the even harmonic signal 112 is not fully synchronized
with the fundamental ballast lamp lighting signal 114. In some
situations this circuit may be used when it is desirable to alter
the synchronization between the even harmonic signal 112 and the
lamp lighting signal 114. This may be accomplished by selecting a
set time difference between the generation of the even harmonic
signal 112 and the fundamental ballast lamp lighting signal 114.
Alternatively, in one embodiment, even harmonic generator 98 is a
variable signal generator, wherein the variability is the timing of
the generation of the even harmonic signal compared to the
generation of the lamp lighting signal. For both situations, and as
shown in FIG. 9, ballast lamp lighting signal 112 is the normally
generated symmetric signal created when the switching network is at
a 50% duty cycle. Then by use of even harmonic generator 98 of FIG.
8, an even harmonic signal 114 is generated which is not
synchronized with the lamp lighting signal 112.
[0036] Turning to FIG. 10, as can be seen in comparison of FIG. 9,
the even harmonic signal 116 is generated at a time different from
that of lamp lighting signal 114 of FIG. 9. Thus, as can be seen,
the even harmonic generator 98 of FIG. 8 can be considered variable
in its generation of the even harmonic signal. By this design, a
variable phase difference (i.e., 118a of FIGS. 9 and 118b of FIG.
10) may be provided between the ballast generated lamp lighting
signal and the even harmonic signal. This variable feature permits
selective control of the amount of offset created in the waveform
of the lamp lighting signal.
[0037] Additionally, in another embodiment shown in FIG. 11,
circuit 120 is designed to include a ballast output sensor 122
which senses the value of the signal being generated by ballast 92.
The output of sensor 122 is supplied to a variable harmonic
generator 98, which may automatically adjust the value of the even
harmonic signal generated by the even harmonic signal generator 98.
It is to be appreciated the output sensor 122 may be any
appropriate sensor which will sense a known output parameter of the
lamp output signal of the ballast, such as but not limited to a
voltage and/or current sensor.
[0038] Additionally, variable harmonic generator 98 may provide its
variability by use of a control circuit 124. For example, in one
embodiment control circuit 124 is designed as a known signal delay
circuit positioned on the primary side 34c or secondary side of
ballast 20. The amount of delay being dependant on the value of the
ballast output signal.
[0039] In this embodiment, even harmonic generator 98 will increase
(or decrease) the value of the even harmonic signal as the ballast
output signal is decreased (or increased), whereby the value of the
even harmonic signal is inversely proportional to the ballast lamp
lighting signal. This operational concept is illustrated in FIGS.
12 and 13. For example, when the ballast supply signal is a 10n
signal, the even harmonic signal 126 may be a 1n signal. Then as
shown in FIG. 13, when the ballast supply signal 112 is sensed to
have been lowered (i.e., dimmed) to 5n, the even harmonic signal is
increased to 2n.
[0040] This arrangement is beneficial to increasing the life of the
lamp, since when the lamp is operating at 100% (e.g., the ballast
signal 10n is the non-dimming 100% ouput) and the formation of
visual striations is less likely, a smaller even harmonic signal
126 may be applied, creating less stress (i.e. lower lamp current
crest factor) on the lamp. However, when a dimming occurs (e.g.,
when the output signal from the ballast is at 5n, showing a dimming
operation), the even harmonic signal may be increased (i.e.,
increased to 2n), in order to eliminate striations which could
otherwise occur due to dimming operations. Thus, by having this
variable capability, when striations are not found to occur, less
stress are put on the lamp, thereby increasing its life
expectancy.
[0041] The present disclosure discusses the use of the fundamental
waveform as the source of the even harmonic signal to be combined
with the lamp lighting signal. Of course, there are other sources
where the signal to be combined with the lamp lighting signal may
be obtained, and it is to be understood it is possible to use a
signal other than the even harmonics signal. Also, while the
primary manner of combining the signals is described as inductive
coupling, the signals can be combined by other well-known signal
merging techniques.
[0042] The even harmonic generator of FIG. 8 and the even harmonic
generator of FIG. 11 can be formed as a single unit, whereby the
variability both in the timing of the generation of the signal
(i.e., FIG. 8) and the value of the even harmonic signal (e.g.,
FIG. 11) are combined in a single even harmonic signal generator.
The described signal generators can be formed using known
technology and therefore do not need to be discussed in greater
detail.
[0043] The described concepts may be employed in dimming and
non-dimming situations and is not limited to a current fed circuit.
Also, while a BJT switching mechanism was shown in FIG. 2, it is to
be appreciated that a system may employ FET switches in the
inverter ballast. As previously noted, the present concepts may be
implemented in numerous forms. In the foregoing embodiment of FIG.
2, component designations and/or values for the circuit of FIG. 3
would include: TABLE-US-00001 Transistor 26 BUL1102E Transistor 28
BUL1102E Zener Diode 30a 68 V Capacitor 30b 0.22 uf Diode 30c
UF4007 Diac 30d 32 V Diode 30e 1N5817 Resistor 30g 150.OMEGA.
Resistor 30h 150.OMEGA. Diode 30i UF4007.OMEGA. Diode 32a
UF4007.OMEGA. Resistor 32f 150 Resistor 32g 150 Diode 32h UF4007
Zener Diode 38a 300 V Zener Diode 38b 300 V Zener Diode 38c 300 V
Capacitor 40 1.2 nf Windings 44 40 mh Windings 46 40 mh Windings 48
80 mh Windings 50 7 mh
[0044] Again, while the present application may be used in a
variety of circuits and embodiments, one such use is for instant
program start ballasts in a family of current fed electronic
ballasts, for example in the 4' T8 electronic design of General
Electric. It is also shown in FIG. 2, that there is no use of an
unbalanced BJT drive winding or impedance in the base drive for the
BJT.
[0045] Although the present concepts are described primarily in
connection with fluorescent lamps, the circuit herein described may
be used to control any type of gas discharge lamp.
[0046] The concepts have been described with reference to the
exemplary embodiments. Obviously, modifications and alterations
will occur to others upon reading and understanding the preceding
detailed description. It is intended that the described concepts be
construed as including all such modifications and alterations.
* * * * *